diff --git a/scripts/_common.sh b/scripts/_common.sh
index ac4de90..0a1e55b 100644
--- a/scripts/_common.sh
+++ b/scripts/_common.sh
@@ -178,9 +178,61 @@ ynh_remove_app_dependencies () {
     ynh_package_autoremove ${dep_app}-ynh-deps	# Remove the fake package and its dependencies if they not still used.
 }
 
+# Check if a mysql user exists
+#
+# usage: ynh_mysql_user_exists user
+# | arg: user - the user for which to check existence
+function ynh_mysql_user_exists()
+{
+   local user=$1
+   if [[ -z $(ynh_mysql_execute_as_root "SELECT User from mysql.user WHERE User = '$user';") ]]
+   then
+      return 1
+   else
+      return 0
+   fi
+}
 
-# Correct the name given in argument for mariadb
-# Avoid invalid characters in your database name
+# Create a database, an user and its password. Then store the password in the app's config
+#
+# After executing this helper, the password of the created database will be available in $db_pwd
+# It will also be stored as "mysqlpwd" into the app settings.
+#
+# usage: ynh_mysql_setup_db user name
+# | arg: user - Owner of the database
+# | arg: name - Name of the database
+ynh_mysql_setup_db () {
+	local db_user="$1"
+	local db_name="$2"
+	db_pwd=$(ynh_string_random)	# Generate a random password
+	ynh_mysql_create_db "$db_name" "$db_user" "$db_pwd"	# Create the database
+	ynh_app_setting_set $app mysqlpwd $db_pwd	# Store the password in the app's config
+}
+
+# Remove a database if it exists, and the associated user
+#
+# usage: ynh_mysql_remove_db user name
+# | arg: user - Owner of the database
+# | arg: name - Name of the database
+ynh_mysql_remove_db () {
+	local db_user="$1"
+	local db_name="$2"
+	local mysql_root_password=$(sudo cat $MYSQL_ROOT_PWD_FILE)
+	if mysqlshow -u root -p$mysql_root_password | grep -q "^| $db_name"; then	# Check if the database exists
+		echo "Removing database $db_name" >&2
+		ynh_mysql_drop_db $db_name	# Remove the database	
+	else
+		echo "Database $db_name not found" >&2
+	fi
+
+	# Remove mysql user if it exists
+        if $(ynh_mysql_user_exists $db_user); then
+		ynh_mysql_drop_user $db_user
+	fi
+}
+
+# Sanitize a string intended to be the name of a database
+# (More specifically : replace - and . by _)
 #
 # Exemple: dbname=$(ynh_sanitize_dbid $app)
 #
@@ -188,7 +240,7 @@ ynh_remove_app_dependencies () {
 # | arg: name - name to correct/sanitize
 # | ret: the corrected name
 ynh_sanitize_dbid () {
-	dbid=${1//[-.]/_}	# Mariadb doesn't support - and . in the name of databases. It will be replace by _
+	dbid=${1//[-.]/_}	# We should avoid having - and . in the name of databases. They are replaced by _
 	echo $dbid
 }
 
diff --git a/scripts/install b/scripts/install
index 5ea0465..8947b94 100644
--- a/scripts/install
+++ b/scripts/install
@@ -60,14 +60,11 @@ db_user="$db_name"
 
 # Generate random DES key & password
 deskey=$(ynh_string_random 24)
-dbpass=$(ynh_string_random)
-ynh_app_setting_set "$app" mysqlpwd "$dbpass"
 ynh_app_setting_set "$app" deskey "$deskey"
 ynh_app_setting_set "$app" db_name "$db_name"
 
 # Initialize database
-ynh_mysql_create_db "$db_name" "$db_user" "$dbpass"
-
+ynh_mysql_setup_db "$db_user" "$db_name"
 #=================================================
 # DOWNLOAD, CHECK AND UNPACK SOURCE
 #=================================================
@@ -92,7 +89,7 @@ wb_conf="${TMPDIR}/app/config/parameters.yml"
 cp ../conf/parameters.yml "$wb_conf"
 ynh_replace_string "{DBNAME}" "${db_name}" "$wb_conf"
 ynh_replace_string "{DBUSER}" "${db_user}" "$wb_conf"
-ynh_replace_string "{DBPASS}" "${dbpass}" "$wb_conf"
+ynh_replace_string "{DBPASS}" "${db_pwd}" "$wb_conf"
 ynh_replace_string "{DESKEY}" "${deskey}" "$wb_conf"
 
 # Install files and set permissions
@@ -118,7 +115,7 @@ done
 exec_console $app "$final_path" fos:user:promote --super "$admin"
 
 # Configure Wallabag instance URL
-ynh_mysql_connect_as "$db_name" "$dbpass" "$db_user"  <<< "UPDATE craue_config_setting SET value = 'https://$domain$path_url' WHERE name = 'wallabag_url'"
+ynh_mysql_connect_as "$db_name" "$db_pwd" "$db_user"  <<< "UPDATE craue_config_setting SET value = 'https://$domain$path_url' WHERE name = 'wallabag_url'"
 
 #=================================================
 # NGINX CONFIGURATION
diff --git a/scripts/remove b/scripts/remove
index 1271ec1..8a942e1 100644
--- a/scripts/remove
+++ b/scripts/remove
@@ -33,8 +33,7 @@ ynh_remove_app_dependencies
 # REMOVE THE MYSQL DB
 #=================================================
 
-ynh_mysql_drop_db "$db_name"
-ynh_mysql_drop_user "$app"
+ynh_mysql_remove_db "$app" "$db_name"
 
 #=================================================
 # REMOVE APP MAIN DIR
diff --git a/scripts/upgrade b/scripts/upgrade
index 6802efd..4cc5529 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -32,7 +32,7 @@ if [ -z "$path_url" ] ; then
   ynh_app_setting_set $app path_url "$path_url"
 fi
 path_url=$(ynh_normalize_url_path $path_url)
-dbpass=$(ynh_app_setting_get "$app" mysqlpwd)
+db_pwd=$(ynh_app_setting_get "$app" mysqlpwd)
 deskey=$(ynh_app_setting_get "$app" deskey)
 final_path=$(ynh_app_setting_get "$app" final_path)
 # Compatibility with previous version
@@ -53,11 +53,15 @@ db_user="$db_name"
 # MANAGE SCRIPT FAILURE
 #=================================================
 
-ynh_backup_before_upgrade # Backup the current version of the app
-ynh_clean_setup () {
-    ynh_backup_after_failed_upgrade
-}
-ynh_abort_if_errors	# Stop script if an error is detected
+# Use prior backup and restore on error only if backup feature
+# exists on installed instance
+if [ -f "/etc/yunohost/apps/$app/scripts/backup" ] ; then
+  ynh_backup_before_upgrade # Backup the current version of the app
+  ynh_clean_setup () {
+      ynh_backup_after_failed_upgrade
+  }
+  ynh_abort_if_errors	# Stop script if an error is detected
+fi
 
 #=================================================
 # INSTALL DEPENDENCIES
@@ -88,7 +92,7 @@ wb_conf="${TMPDIR}/app/config/parameters.yml"
 cp ../conf/parameters.yml "$wb_conf"
 ynh_replace_string "{DBNAME}" "${db_name}" "$wb_conf"
 ynh_replace_string "{DBUSER}" "${db_user}" "$wb_conf"
-ynh_replace_string "{DBPASS}" "${dbpass}" "$wb_conf"
+ynh_replace_string "{DBPASS}" "${db_pwd}" "$wb_conf"
 ynh_replace_string "{DESKEY}" "${deskey}" "$wb_conf"
 
 # Replace files and set permissions
@@ -103,7 +107,7 @@ exec_console $app "${final_path}" doctrine:migrations:migrate
 exec_console $app "${final_path}" cache:clear
 
 # Configure Wallabag instance URL
-ynh_mysql_connect_as "$db_name" "$dbpass" "$db_user"  <<< "UPDATE craue_config_setting SET value = 'https://$domain$path_url' WHERE name = 'wallabag_url'"
+ynh_mysql_connect_as "$db_name" "$db_pwd" "$db_user"  <<< "UPDATE craue_config_setting SET value = 'https://$domain$path_url' WHERE name = 'wallabag_url'"
 
 #=================================================
 # NGINX CONFIGURATION